Process for preparing thymol



Patented Nov. '11, 1932 UNITED sures PATENT curios.

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am) ARTHUR ssamr, or D'UssnLmnr-mm'r, GERMANY, assmnoas ro mmrscim WEB-I'm GISELLBCHAIT DUSSELDOBF-OBEBKASSEL, GERMANY- MIT BEBCHBANKTER- HAF'FUNG, OI

raocnss roa rmmme airmen Ho Application mod June 80, 1928, Serial No. 289,619, and in Germany July 11, 1927.

The present invention relates to a process for preparing thymol by combining propy lene with m-ereso We have discovered the surpnsmg fact that pro ylene and m-cresol may be caused to com ineto form ropyl or isopropyl denva tives of m-cresol 8 simply heating them together, to fairly 'gh tem ratures under pressure.. The reaction con 'tlonscan so 1o chosen that the main roduct of the combination of propylene an m-cresol 1s thymol (3- hydroxy 1 me'thyl- 4 isopropyl-benzene) Temperatures from about 300 C. to 4 009 C. are with advantage employed. The pressure w. at which the combination. of the'pgogiylene with the m-cresol is' efiected must gher than the vapour pressureor the decomposition-pressure of the reaction product at the temperature employed. Molecular propor- M tions of propylene and m-cresol are, m general, employed. An excess of m-cresol represses, and 'anexcess of ropylene promotes, the formation of multiple propylated addi-' tion products.

35 We have further found that the condensation of prep lene with m-cresol as described above, may effected in a technically more simple manner, with the aid of catalysts, as the temperature the pressure and the reac- 30 tion period are decreased thereby. The combination of the-propylene with m-cresol can in this wa be effected at normal pressure and even at re uced pressure. A large number of substances of 'the most varied kinds can be employed as catalysts for thereaction m'question. The usual condensing agents and sub-' stances which bring about'the splitting oil of water are particularly suitable, for example, inorganic and organic acids and their derivatives, for example, sulphuric acid, hydrochloric acid, the various phosphoric acids,

sulphonic acids, phosphoric anhydride, phosphoric acid chloride and the like. A 45 Metal oxides, for example, aluminum oxide, thorium oxide, tungstic oxide and the like.

Metal salts, for example, zinc chloride,

aluminum chloride, 'ferric chloride, magnesium chloride, potassium .bisulphate, potash 50 alum, aluminum sulphate, aluminum phoshydroxy-1-methyl-2-isopropyl-benzene) havphate, aluminum silicate, other metallic silicates andthe like.

Contact substances, for example, active charcoal, silica gels, kieselguhr, kaohn, clay, fullers earths, bleaching earths, sihceous earths and the hydrosilicates obtained from the above-mentioned silicates by the, action of acids and the like.

The catalysts may be employed in several difierent ways, either alone or mixed .with one another or deposited 'on carriers, which may consist of any of the above-mentioned contact substances or of other substances, for

examglqpumice stone, barium sulphate and the li e; l V Y The action of the catalysts on the condensation varies. The temperature, pressure and period of reaction have, therefore, to be va ried according to theicatal ic action. The exam les illustrate the re erred method of, proce ure for individu cases.

The reaction product obtained in the de-' scribed. condensation of pro ylene with rn-cres ol with and without the ai of catalysts is sub ected to fractional distillafion in order to separate the thymol from the by-products. The first fractions coming over consist of unchanged m-cresol and, accordin to the reactlon conditions, an isomer ofymol (8- so mg a melting 8 int of 69 C. and a boilin mt of 228 .to 229 C. From the mi 1e and main fraction of the fractional distillation th 01, having a boiling oi-nt of 232 C. an a melting point of 51 .,.is obtafilzfid- The ifieiat fractlions' 'eilg an isomer 0. ymo 3- y roxy- -met y r -isopropy benzene) oi melting point 114 C. and-boil 1n point 245 C. to 246 C. and also di-propy -oriso ropyl-m-cresols having a boiling point of a ut 265 C. Accordin to the reaction conditions derivatives 0 m-cres'ol propylated at the oxy n atom, for example, lsoprgpyl-m-cres 1" et er of boilin point 196 1. tie 197; di iland tlaelliiglllier b0 u pro'py -t ymo at or an ig er propy a m-cresol others-are obtained... If those others should be present they are separated in known. manner fromthe phenol by treatipf the reaction product with dilute-caustica catalyst. at about 150 C. to 350 C. contact substance or catalyst may, for ex:

-kalies and the henol mixture mol is obtained as the main product and t by-products mentioned onl in subordinate quantities,'as is shown in t e following cx-' amples 1. 108' parts by weight of m-crcsol are heat ed in a pressure apparatus, such as a pressure tube, autoclave or the like, with 3540 parts by weight of propylene undera pressure of about 30 to 40 atmospheresat a temperature of about 330 C. to 350 C. for 20-40 hours. The reaction product is then fractionally distilled and the thymol boiling at 232 C. sepa rated and recrystallized from benzine. A pure product having a melting point of 51 C. is obtained. Taking into consideration the m-cresolrecovercd during the distillation, thymol is obtained in a yield of 50-60% of the m-cresol'reacted upon. I

2. m-cresol vapour'is passed together with propylene at normal or reduced pressure nlvler 1e ample, be aluminum oxile, which is shaped or ressed into pieces w ilst in a moist conditlon and then dried. As catalyst there may also be employed, thorium oxide mounted on pumice, aluminum phosphate or aluminum ydroxide deposited on kieselguhr, active charcoal containing phosphoric acid or zinc chloride, brick clay, fullers earths or one of the activated bleaching earths used in commerce, preferably in the form of pieces about the size of a bean, The speed at which the reacting substanceslare passed through one of the usual contact apparatus is so regu-' lated that as high a yield of thymol aspossible is obtained. -The rate of passage alsodepends onthe nature of the catalyst employed, the length and volume of the contact space and the reaction temperature. The

amount of propylene passed through apparatus. is such-that anexcess of propylene leaves the apparatus together with the condensation product. Any alkali-insoluble ethers (iso'propyl-m-cresyl ether and isopropyl-thymol -ether and higher propylated mcresyl ethers) present arescparated from the condensation product by treating the latter with dilute caustic soda. On acidifying the alkaline solution an ether-free phenol mixture is obtained. I The latter or the ether-free condensation. product is fractionallydistilled.

- .About 60% of the m-cresol employed is recovered in thefirst fraction. A small-fraction can be collected fromwhich the isomer of thymol having a melting point of 69 C. and aboiling point of from 228 C. to 229 G. separates out. The next and larger fraction contains the thymol having a boiling point of 232 C., which separates out on cooling 05. and which can be obtained pure with a melt- The iso er of thymol having a melting point of 14. G. and "a boiling point 245 C.-246; C. crystallizes out from the final fraction. The residue-an oil .boilin at" about 265 C.consists of 'a mixture '0 va-' rious di-propylor -isopropyl m-cresols. The yieldin thymol amounts to about 50% to 60% of the m-cresol reacted.

3. 108 parts by weight of m-cresol are.

treated in an autoclave with 35 to 40 parts by weight of propylene at a pressure ofabout '5 to 30 atmospheres and a temperature of about 180 C. to 230 C. for about 15 tov hours with stirring in the presence of about IO-parts b weight of a catalyst. About 100% sulp uric acid or the m-cresol sulphonic acid formed from the sulphuric acid and the m-cresol or anhydrous zinc chloride, or phosphoric anhydride or about, 100% phosphoric acid or an activated bleaching earth may be, for example, employed as the catalyst. The reaction product isse arated from the catalyst by. steam distillation, by 'suctional filtration, by centrifuging or shak ing out with water and is then fractionally distilled whereby the thymol and the b products are obtained as in Example 2 in t e different fractions.

In the following further'exam le it will now be shown that with the aid 0 a few of the catalysts mentioned a condensation of the substances mentioned may be effected at temperatures of about 100 C. and even lower.

t was, however, found that in this case the combination or condensation of propylene,

with m-cresol is efiected in such a manner that the by-products mentioned are chiefly obtained and thymol scarcely formed or only formed'in small quantities. If, however, in this case the treatment after the condensation is continued at'higher temperatures or if the condensation is carried out at a higher temperature from the start for a sufiiciently long time a maximum yield of thymol is obtained.

4. 108 arts by weight of m-cresol are condensed with to 40 parts'by weight of propylene in the resence of about 10 parts by wei ht of cata ysts, for example, about 100% 'sulp uric acid'at a temperature of about C. to C. and a pressure of 2 to 10 atmospheres with stirrlng for several hours. On working up the reaction product according to Examp e ties of t ymol are formed. however, the condensation product is further heated to about 220 C. for about 20 hours with stir-- s 2 and 3 the by-products of 1 thymol reponderate and only small quantiand subjecting thereaction product obtained to fractional distillation.

2. A process for preparing thymol which consists in causing propylene to react with m-cresol at temperatures from to 400 C. and increased pressure and subjecting the reaction product obtained to fractional distillation.

3. A process for preparing thymol which consists in causing propylene to react with m-cresol at temperatures from 100 to 400 .C. in the presence of condensing and dehydrating catalysts and subjecting the reaction 1 product obtained to fractional distillation.

4. A process for preparing thymol which consists in causing propylene to react with m-cresol at temperatures from 100 to 400 C. and increased ressure in the presence of condensing and ehydratin catalysts and subjecting the reaction pro not obtained to fractional distillation.

-5. A process for preparing thymol which consists in causing propylene to react with m-cresol at temperatures from 100 to400 C. and increased. pressure in the presence of Y acidic condensing and dehydrating catalysts and subjecting the reaction product obtained to fractional distillation.

6. A process for preparing thymol which consists in causing propylene to react with m-cresol at temperatures from 100 to 400 0., treating the condensation product with dilute caustic alkalis,'separating the alkaliinsoluble ethers from the alkaline solution,

acidifying the alkaline solution and subjecting the phenol mixture thus obtained to fractional distillation.

In testimony whereof we have signed our names-to this specification.

SIEGFRIED SKRAUP. KARL SCHULLKOPF. ARTHUR SERINI. 

